The production of restorative objects such as crowns, bridges and tooth prostheses requires use of dental models from which to work. Such models are created using a negative impression of the teeth. The negative impression is then filled with casting materials which harden, thus creating models of the patient's teeth. In order to work with these models, the casting material must be sawed into smaller pieces. It is essential to be able to realign the pieces in the appropriate manner.
In making of models, the technician uses a device known as an articulator, which is an instrument which simulates the movements of the mandible and aids in the construction of dental restorations.
The prior art includes several devices for use in making the models. U.S. Pat. No. 4,398,884 to Huffman, which describes an insert which locks onto the casting material to guide removal of model teeth during insertion into and withdrawal from the dental model presents an approach to the need to divide, then reassemble the models. However, the devices disclosed therein do not provide means for relating the maxillary and mandibular dental arches with one another in such a way as to create an accurate three-dimensional model showing the arches as they were at the time the impression was made.
Another apparatus for creating dental models is disclosed in U.S. Pat. No. 4,708,835, to Kiefer, wherein a base plate containing a plurality of pre-formed holes is fitted with dowel pins in each location where it is desired to make a die removable from a cast dental arch. Two methods of determining which of the pre-formed holes in a base plate are to have dowel pins inserted in them are disclosed. One version requires the use of a transparent datum plate which is positioned over the base plate and fitted with marker pins at desired locations. The data plate is then removed from the carrier plate, flipped over and remounted on the opposite side of the upright of the carrier plate. The base plate is then mounted to the upright of the carrier plate, over the data plate, and dowel pins are inserted into preformed holes in the base plate at those positions occupied by marker pins in the underlying data plate. Both datum plate and base plate with dowel pins inserted are then removed from the carrier plate, and the base plate is again flipped over and remounted to the opposite side of the carrier plate upright over a dental impression containing freshly poured liquid die stone, and pushed downward so the base plate contacts the impression.
U.S. Pat. No. 4,371,339 to Zeiser, requires the use of a complicated and expensive orienting apparatus which has been manufactured to precise tolerances for holding a dental impression while determining the locations on a prefabricated base plate where holes are subsequently to be made for securing dowel pins which will be molded into a dental arch.
Whelan, in U.S. Pat. No. 4,439,151, describes a method to facilitate the mounting and dismounting of individual teeth by use of a central plastic insert member having projecting elements through the base of the tray to facilitate removal by pushing on said projection portions. The devise also includes a means to pivot the trays apart to 180 degrees to provide filling of both tray and impressions. A shortcoming of this device is that a model of only the mandibular or maxillary arch can be made. The model must then be removed from one member of the device and inserted into the second member before work on the model can be accomplished.
U.S. Pat. No. 5,466,152 to Walter discloses and claims a dental articulator system containing a plurality of holes in the tray support into which pins are inserted before the casting material is placed into the tray. The pins provide indexing means for reassembly of the model after it has been divided into smaller pieces. The trays having multiple holes for insertion of indexing pins are more difficult to make than the trays of the instant invention. Furthermore, they do not allow for the broad discretion in placement of pins that is available when the reciprocating acceptor region is one continuous opening in the tray.
PCT Application PCT/US99/16508 of Walter discloses a tray support having an opening into which a protrusion from a tray is inserted. However, that disclosure does not teach use of a continuous opening that will accept pins, nor is the opening appropriate for use wherein stone is allowed to enter into the opening in the tray support. The use of that device requires that the model rest on the tray in the support. While the method of that disclosure provides a stable model, cutting through the tray requires very strong saws.